[NA] Residential HVAC - can 'system' SEER be higher than component SEER?

Van Johnston

Van Johnston

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Van Johnston
I know there are a lot of HVAC-savvy guys on here. Help me out please.

Replacing 17 y.o. 3.5 ton unit. Contractor gave me a quote for 15 SEER system. (He quoted a 16 also). I asked for model numbers, and the unit product data sheet I found on-line clearly says it is rated at 14 SEER. I asked the guy to confirm the model he specified is the 15 SEER model. His answer was the SEER rating is a combination of indoor unit + outdoor + coil. Doesn't make sense to me that you could coax an efficiency out of the system higher than any component. What am I missing?
 
System efficiency is affected by indoor and outdoor coil size; the larger the coil(s) the more efficient the system. Your new outdoor unit is rated when used with a particular size indoor coil. If your indoor coil is larger than this, it will be more efficient.
 
Yes it can be higher than the rating one of the components. SEER is a composite rating of the system as a whole. Not uncommon for the system SEER to be greater than that stated on the outdoor unit.

Ask to see the rating of the system as a whole from the manufacturer or AHRI.
 
"ton unit"

That must be the maddest unit of measurement on the planet, it's a unit of power. I don't dispute its convenience for making comparisons, but dear FSM! Less convenient for answering say, how much will it cost to operate? Let's see, what's the latent heat of fusion of water ...

"The rate of heat transfer that results in the freezing or melting of 1 short ton (2,000 lb; 907 kg) of pure ice at 0 °C (32 °F) in 24 hours."
 
Actually the ton unit made perfect sense long ago. Before mechanical air conditioning was practical, some rich people would cool their house with ice, much like the "ice box" used to keep food cool. The tons of ice used per day was a convenient measure.
For calculations, multiply the ton rating by 12,000 to get BTU/hr.
 
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